We've changed our CVS server from GNU CVS 1.11.21 to GNU CVS 1.12.13. Now committing changes with enabled compression (in SmartCVS) is impossible, because the CVS server does not respond. We've tried other GNU CVS versions and following are working: 1.11.14, 1.11.21, 1.12.9. It appears to be a problem with the zlib, which contains an incompatible change.